In recent years, charged particle beam devices such as an electron microscope are used in observation and analysis of samples having fine tissue structures. In general, a sample chamber in which a sample is disposed is evacuated to make a sample atmosphere in a vacuum state in these devices.
However, in a case where most part of a sample is occupied with water such as a biological sample, the volume is contracted due to evaporation of water in the sample in the vacuum state and an internal structure may vary largely. As one of treatments for observing the fine structure of such sample as close as possible to the original state, a method of fixing the sample instantly by quick freezing.
In Patent literature 1 (JP-A-2013-88328), there is disclosed a method of fabricating an observation sample for a transmission electron microscope (TEM) by performing freeze-substitution with respect to various forms of samples such as liquid and gelatinous forms after quick freezing.
The samples subjected to treatment such as freezing (hereinafter collectively referred to merely as “cooled samples” in some cases) are introduced into a charged particle device after conveyed to a sample holder.
As a technique for effectively observing the cooled sample conveyed to the sample holder, Patent Literature 2 (JP-A-2010-257617) discloses a technique in which a shutter member shutting between a cooling mechanism and the outside is provided in the sample holder and a series of work from cooling treatment to observation of the sample is executed in one sample holder. Furthermore, in Patent Literature 3 (JP-A-2014-10965), a sample holder keeping a posture of a cooling source stably regardless of inclination of the sample is explained.